ABSTRACTS OF TECHNICAL PAPERS 811 



temperature of the conductor, R(w) is the real component of impedance 

 of the conductor, F(co) is the transfer impedance of the amphfier, and 

 co/27r = / represents frequency. The value of Boltzmann's constant 

 obtained from the measurements lies near the accepted value of this 

 constant. The technical aspects of the disturbance are discussed. 

 In an amplifier having a range of 5,000 cycles and the input resistance 

 R, the power equivalent of the effect is V'^/R = 0.8 X lO"^" watt, 

 with corresponding power for other ranges of frequency. The least 

 contribution of tube noise is equivalent to that of a resistance Re = 1-5 

 X lOHp/jji, where ip is the space current in milliamperes and ju is the 

 effective amplification of the tube. 



The Voltage- Current Relation in Central Cathode Photoelectric Cells }- 

 Thornton C. Fry and Herbert E. Ives. This paper presents a 

 theoretical basis for the interpretation of the experimental results 

 described in the paper which follows. It considers a source of 

 photoelectrons located on the inner of two concentric spheres; 

 derives the trajectory of an electron shot off at any angle with any 

 speed; and then makes use of this information to compute the current 

 which would be received by a small collector located anywhere on the 

 outer sphere upon very general assumptions as to the directional 

 distribution and velocity distribution of the photoelectrons. This 

 theoretical study is followed by graphical presentation of results com- 

 puted for several typical cases of special interest in connection with the 

 experimental study. 



The Distribution in Direction of Photoelectrons from Alkali Metal 

 Surfaces}^ Hervert E. Ives, A. R. Olpin and A. L. Johnsrud. 

 An experimental study of the distribution in direction of photoelectrons 

 emitted from alkali metal surfaces irradiated by light incident at 

 various angles and polarized in different planes. The alkali metal 

 surfaces used were of two sorts: (1) liquid alloys of sodium and po- 

 tassium, (2) thin films of potassium or rubidium on polished platinum. 

 In all cases the alkali metal surface was at the center of a large spherical 

 enclosing anode, provided either with collecting tabs at various angular 

 positions or with an exploring finger. It is found that the emission 

 closely obeys Lambert's law, but that the ellipse by which the emission 

 is represented, in polar coordinates, is more elongated normally to 

 the surface for perpendicularly incident light than for obliquely, when 

 the direction of the electric vector is in both cases parallel to the 

 surface, and still more elongated for obliquely incident light with the 



^^ Physical Review, Vol. 32, No. 1, pp. 44-56, July, 1928. 

 ^^ Physical Review, Vol. 32, No. 1, pp. 57-80, July, 1928. 



